Will a 1972 chevelle body fit a 1978 cutlass frame?

no, they are similar in design, but entirely different.

78-88 frames are known as "metric frames" as they have all fasteners attached to them as being metric. 78-80 are A body, and 81-88 are known as G bodies. Interchange beteween the 68-72 generation and 78-88 generation is limited to engine, trans, steering box bolt up, and perhaps radiator.

thanks for the info, battery had done some damage to the original frame, nothing that cant be fixed but a friend of mine had a cutlass frame in mint shape from another project. They looked very similar. Guess ill just patch up the old one.